Sucked material detector, sucked material detecting method using the same detector, shift detecting method using the same detector, and cleaning method using the same detector

ABSTRACT

The present apparatus includes an attracting transport arm for attracting an attraction object via a nozzle hole by vacuum and transporting the attraction object in a horizontal or vertical direction. An upwardly directed light emitting sensor is disposed on the rear side of a portion of a stage at which the attraction object is to be placed. At the location at which the attraction object is to be placed, a through-hole which is intended to prevent interception upward rays of light of the light emitting element is perforated. Meanwhile, a downwardly directed light receiving element for receiving rays of light from the light emitting element is disposed in the interior of the nozzle hole of the attracting transport arm.

TECHNICAL FIELD

This invention relates to an attraction object detection apparatus andan attraction object detection method which can detect whether or not anattraction object is present, and more particularly to an attractionobject detection apparatus and an attraction object detection methodsuitable for use with an IC test handler which has an attractingtransport arm.

BACKGROUND ART

Conventionally, an attraction object to be transported by an attractingtransport arm is detected using, for example, a pressure sensor or atransmission type sensor.

Therefore, an attraction object detection apparatus which employs apressure sensor is shown in (a) and (b) of FIG. 1 while anotherattraction object detection apparatus which employs a transmission typesensor is shown in FIG. 2, and their constructions and operations aredescribed.

The apparatus shown in FIG. 1 is constructed such that it includes anarm 2 having a suction opening and movable in a horizontal direction anda vertical direction and air around the suction opening of the arm 2 issucked into a vacuum source (not shown) via a pressure sensor 3. In thepresent apparatus, whether or not an attraction object 1 is present isdiscriminated by a pressure sensor 3 when the arm 2 is moved down to alocation at which the attraction object 1 is to be placed. Inparticular, if the attraction object 1 is not present when the arm 2 ismoved down, since the suction opening of the arm 2 remains in a leakingcondition, a drop of pressure is not detected by the pressure sensor 3,but if the attraction object 1 is present, then there is no leak fromthe arm 2 and a drop of pressure is detected by the pressure sensor 3.From this, whether or not the attraction object 1 is present can bediscriminated.

Meanwhile, in the apparatus shown in FIG. 2, a transmission type sensoris disposed at a location at which an attraction object 1 is to beplaced. In the transmission type sensor, rays of light which go acrossthe location at which the attraction object 1 is to be placed are formedfrom a pair of light emitting elements 4 and a pair of light receivingelements 5. In the apparatus of the type just described, whether or notan attraction object 1 is present can be discriminated as the attractionobject 1 intercepts rays of light between the pair of light emittingelements 4 and the pair light receiving elements 5 of the transmissiontype sensor.

However, such an apparatus as shown in FIG. 1 is disadvantageous in thatwhether or not an attraction object is present cannot be discriminatedunless the arm is moved down to the location at which the attractionobject is to be placed. The apparatus is disadvantageous also in that itmay possibly discriminate in error that an attraction object is presentbecause of an error in adjustment of the pressure sensor.

On the other hand, such an apparatus as shown in FIG. 2 isdisadvantageous in that it cannot be used where the sensor cannot bemounted in horizontal and oblique directions with respect to anattraction object. The apparatus is disadvantageous also in that, whereit is intended to discriminate whether or not an attraction object ispresent at each of a large number of attraction points, a large numberof sensors are required.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide an attraction objectdetection apparatus and method which is superior in throughput to theconstructions of the prior art described above, can detect withcertainty whether or not there is present an attraction object, and inwhich the required space is reduced and is simple in construction.

In order to attain the object described above, the present inventionpresupposes an attraction object detection apparatus for detectingwhether or not an attraction object to be attracted and transported byan attracting transport arm which is movable in vertical and horizontaldirections is present at a predetermined location of a stage. And, afirst aspect of the present invention is characterized by the followingpoints. In particular, the attracting transport arm has a nozzle holeformed therein in such a manner as to be opened toward the stage sideand communicated with a vacuum source. A light emitting element isdisposed either on the rear side to the predetermined location or on theattracting transport arm. The stage has a through-hole provided at thepredetermined location such that rays of light from the light emittingelement may not be intercepted by the stage. And, a light receivingelement for receiving the rays of light from the light emitting elementis disposed on the rear side to the predetermined location or theattracting transport arm at which the light emitting element is notdisposed. Particularly, the light emitting element or the lightreceiving element is preferably disposed in the interior of the nozzlehole of the attracting transport arm.

Meanwhile, a second aspect of the present invention is characterized bythe following features. In particular, a reflection element is disposedeither on a surface of the stage at the predetermined location or on theattracting transport arm. And, a light emitting element and a lightreceiving element for receiving rays of light from the light emittingelement via the reflection element are disposed on the surface at thepredetermined location or the attracting transport arm at which thereflection element is not disposed. Particularly, either the lightemitting element and the light receiving element in pair or thereflection element is preferably disposed in the interior of the nozzlehole of the attracting transport arm.

In those apparatus, an upper portion of the attracting transport armincluding the light emitting element or the light receiving element orelse the reflection element or a set of a light emitting element and alight receiving element disposed in the interior of the nozzle hole mayform a sensor unit independent of but connectable to the attractingtransport arm by an optical fiber. Or, the sensor unit independent ofthe attracting transport arm may be secured at a position opposing thepredetermined location while the attracting transport arm is sostructured as to allow rays of light from the light emitting element topass thereto.

A third aspect of the present invention provides an attraction objectdetection method which uses the apparatus according to the first orsecond aspect of the present invention described above, characterized inthat, when the attracting transport arm is moved to a position above thepredetermined location, if the light receiving element receives nolight, then it is determined that an attraction object is present, butif the light receiving element receives light, then it is discriminatedthat no attraction object is present.

In this method, preferably a vacuum pressure sensor is provided in avacuum line from the nozzle hole of the attracting transport arm to thevacuum source, and after it is discriminated by the light receivingelement that an attraction object is present, the attracting transportarm is moved downwardly to the predetermined location and performs anattraction operation to confirm presence or absence of the attractionobject again by means of the vacuum pressure sensor.

A fourth aspect of the present invention provides a positionaldisplacement detection method for detecting positional displacement ofan attracting transport arm using an apparatus according to the first orsecond aspect of the present invention, characterized in that, when theattracting transport arm is moved from a reference position to aposition above the predetermined location while an attraction object isnot present at the predetermined location, if the light receivingelement does not receive rays of light from the light emitting element,then it is determined that the position of the attracting transport armis displaced from the predetermined position. In this instance,preferably, after it is determined that the position of the attractingtransport arm is displaced from the predetermined location, theattracting transport arm is horizontally moved in an arbitrary directionuntil the light receiving element receives the rays of light from thelight emitting element, and coordinates of the position to which theattracting transport arm is to be moved upwardly above the predeterminedlocation are corrected based on coordinates of a position recognized bymoving means for the attracting transport arm when the light receivingelement receives the rays of light.

A fifth aspect of the present invention provides a cleaning method whichuses an apparatus according to the first or second aspect of the presentinvention described above, characterized in that positive pressure airis supplied into a vacuum line from the nozzle hole of the attractingtransport arm to the vacuum source to blow out the air from the nozzlehole toward the predetermined location.

A sixth aspect of the present invention provides an attraction objectdetection apparatus, characterized in that a proximity sensor isdisposed at the predetermined location.

A seventh aspect of the present invention provides an attraction objectdetection apparatus, characterized in that distance detection means formeasuring a distance to an object present in an opposing direction isdisposed on the attracting transport arm. And, an attraction objectdetection method according to this apparatus is characterized in thatpresence or absence of the attraction object is determined from the factthat the distance detected by the distance detection means is differentwhether the object is the attraction object or the stage, and also adistance of downward movement of the attracting transport arm isrecognized by the distance detection means.

BRIEF DESCRIPTION OF DRAWINGS

(a) and (b) of FIG. 1 are schematic views showing an example of aconventional attraction object detection apparatus which employs apressure sensor;

FIG. 2 is a schematic view showing an example of a conventionalattraction object detection apparatus which employs a transmission typesensor;

FIG. 3 is a schematic sectional view showing an embodiment of anattraction object detection apparatus and method of the presentinvention;

FIG. 4 is a schematic sectional view showing another embodiment of anattraction object detection apparatus and method of the presentinvention;

FIG. 5 is a schematic sectional view showing a further embodiment of anattraction object detection apparatus and method of the presentinvention;

FIG. 6 is a schematic sectional view showing a still further embodimentof an attraction object detection apparatus and method of the presentinvention; and

FIG. 7 is a schematic sectional view showing a yet further embodiment ofan attraction object detection apparatus and method of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention are described below withreference to the drawings.

FIG. 3 is a schematic sectional view showing an embodiment of anattraction object detection apparatus and method of the presentinvention. The apparatus of the embodiment shown includes an attractingtransport arm 12 for attracting and transporting an attraction object 11in horizontal and vertical directions. More particularly, the attractingtransport arm 12 has a nozzle hole opened downwardly. An outlet port forextracting air from the nozzle hole to a vacuum source (not shown) isdisposed at a side portion of the arm 12. Consequently, when the vacuumsource operates, the attraction object 11 can be attracted to theopening end of the nozzle hole.

The attraction object 11 is scheduled to be placed on a stage 13, and anupwardly directed light emitting sensor 14 is disposed on the rear sideof the location of the stage 13 at which the attraction object 11 is tobe placed. At the location of the stage 13 at which the attractionobject 11 is to be placed, a through-hole is opened so that it does notinterrupt upward rays of light from the light emitting sensor 14.Meanwhile, a downwardly directed light receiving sensor 15 for receivingrays of light from the light emitting sensor 14 is disposed in theinterior of the nozzle hole of the attracting transport arm 12. Thelight receiving sensor 15 and the light emitting sensor 14 in pairconstruct a so-called transmission type sensor. It is to be noted thatthe light receiving sensor 15 in the attraction nozzle hole may becovered with a transport element 16. Further, the light emitting sensor14 may be disposed on the attracting transport arm side while the lightreceiving sensor 15 is disposed on the stage side. Or, the lightemitting sensor 14 or the light receiving sensor 15 may be mounted on anouter side of the attracting transport arm 12.

In the apparatus of the form described, the attracting transport arm 12is first moved to a location above the location of the stage 13 at whichthe attraction object 11 is to be placed. In this instance, if theattraction object 11 is present on the stage 13, then the attractionobject 11 intercepts upward rays of light from the light emitting sensor14. Consequently, the light receiving sensor 15 in the attractingtransport arm 12 does not react. From this, it can be discriminated thatan attraction object is present. Therefore, the attracting transport arm12 is moved downwardly, attracts the attraction object 11 thereto and isthen moved upwardly as in an ordinary operation. On the other hand, ifthe attraction object 11 is not on the stage 13, then the rays of lightfrom the light emitting sensor 14 on the rear side of the stage 13 cometo the light receiving sensor 15 in the attracting transport arm 12, andconsequently, the light receiving sensor 15 reacts. From this, it can bediscriminated that no attraction object is present, and also the movedposition of the arm is confirmed. Further, in the apparatus of theconstruction just described, even if downward movement of the attractingtransport arm 12 is not performed, whether or not there is present anattraction object can be confirmed. Accordingly, since no uselessdownward or upward movement is involved, the apparatus is improved inthroughput comparing with the prior art shown in FIG. 1.

Further, in the present embodiment, if air of a positive pressure issupplied to a vacuum line extending from the nozzle hole to the vacuumsource, then the air can be blown from the nozzle hole to the uppersurface of the light emitting sensor 14 on the rear side of the stage13, to which dust or like foreign articles are liable to stick, to cleanthe sensor readily.

However, in the present embodiment, since it is discriminated that anattraction object is present when the light receiving sensor 15 does notreceive rays of light from the light emitting sensor 14, if the stoppingposition of the arm 12 is displaced from the light emitting sensor 14,the sensor may discriminate in error that an attraction object ispresent although the attraction object 11 is not present on the stage13. In this instance, if such a pressure sensor as shown in FIG. 1 isprovided for the vacuum line from the nozzle hole to the vacuum source,such positional displacement of the arm as described above can bediscriminated by the pressure sensor. In particular, the positionaldisplacement of the arm can be discriminated if it is discriminatedagain by means of the pressure sensor whether or not the attractionobject 11 is present after the attracting transport arm 12 is moveddownwardly to perform an attracting operation.

Further, even if a pressure sensor is not used but another sensor or alike element which can detect a thickness of an attraction object or adistance to an attraction object is used, it is possible to confirmwhether or not there is present an attraction object and positionaldisplacement of the arm.

The present invention is not limited to the form described above and mayhave such various forms as described below. FIGS. 4 to 7 are schematicsectional views of other embodiments of the attraction object detectionapparatus and method of the present invention. In the description of theother embodiments and the drawings, the same components as those of theembodiment described above are denoted by the same reference numeralsand overlapping description is omitted.

In the apparatus of the form shown in FIG. 4, a reflection element 17 isdisposed on the surface of the location of the stage 13 at which theattraction object 11 is to be placed. Further, a reflection type sensorformed from a light emitting sensor 14 and a light receiving sensor 15in pair is disposed in the interior of the nozzle hole of the attractingtransport arm 12. It is to be noted that the reflection type sensor inthe nozzle hole may be covered with a transport element 16. Further, thelight emitting sensor 14 and the light receiving sensor 15 in pair maybe disposed on the stage side while the reflection 17 element isdisposed on the attracting transport arm side. Or, either the lightemitting sensor 14 and the light receiving sensor 15 in pair or thereflection 17 may be mounted on an outer side of the attractingtransport arm 12.

Also in the apparatus of the present form, the attracting transport arm12 is first moved to a location above the location of the stage 13 atwhich the attraction object 11 is to be placed. In this instance, whenthe attraction object 11 is present on the stage 13, the reflectionelement 17 is covered with the attraction object 11. Consequently, thelight receiving sensor 15 in the attracting transport arm 12 does notreact. Since it can be discriminated from this that an attraction objectis present, the attracting transport arm 12 is moved downwardly,attracts the attraction object 11 and is then moved upwardly as in anordinary operation. On the other hand, when the attraction object 11 isnot present on the stage 13, rays of light from the light emittingsensor 14 are reflected by the reflection element 17 and come to thelight receiving sensor 15, and consequently, the light receiving sensor15 reacts. From this, it can be discriminated that no attraction objectis present and also the moved position of the arm can be confirmed.Further, in the apparatus just described, since no useless downward orupward movement is involved, the apparatus is improved in throughputcomparing with the prior art shown in FIG. 1, similarly as in the formdescribed above.

Further, also in the present form, if air of a positive pressure issupplied to a vacuum line extending from the nozzle hole to the vacuumsource, then the air can be blown from the attraction nozzle to theupper surface of the reflection element 17 on the stage 13 to clean thesensor readily.

However, also in the present form, since it is discriminated that anattraction object is present when the light receiving sensor 15 does notreceive reflected rays of light of the light emitting sensor 14 from thereflection element 17, if the stopping position of the arm 12 isdisplaced from the light emitting sensor 14, the sensor may discriminatein error that an attraction object is present although the attractionobject 11 is not present on the stage 13. In this instance, if such apressure sensor as shown in FIG. 1 is provided for the vacuum line fromthe nozzle hole to the vacuum source, such positional displacement ofthe arm as described above can be discriminated by the pressure sensor.In particular, the positional displacement of the arm can bediscriminated if it is discriminated again by means of the pressuresensor whether or not the attraction object 11 is present after theattracting transport arm 12 is moved downwardly to perform an attractingoperation.

Further, even if a pressure sensor is not used but another sensor or alike element which can detect a thickness of an attraction object or adistance to an attraction object is used, it is possible to confirmwhether or not there is present an attraction object and positionaldisplacement of the arm similarly as in the form described above.

In addition to the two forms described above, the present invention maybe an apparatus wherein an upper portion of the attracting transport arm12 shown in FIG. 3 or 4, that is, the sensor arrangement in the interiorof the nozzle hole (where a transmission type sensor is used, only thelight receiving sensor, but where a reflection type sensor is used, aset of light emitting and light receiving sensors), is formed as asensor unit 19 independent of the attracting transport arm 12 as shownin FIG. 5, and the sensor unit 19 and the nozzle hole of the attractingtransport arm 12 are connected to each other by an optical fiber 18.

Or, the present invention may be an apparatus wherein, as shown in FIG.6, such a sensor unit 19 as described above is fixed in an opposingrelationship to the light emitting sensor 14 on the rear face of thestage 13 shown in FIG. 3 or to the reflection element 17 on the stage 13shown in FIG. 4. It is to be noted that, in this instance, the interiorof the nozzle hole extends through up to the upper end of the attractingtransport arm 12 so that rays of light of the sensor may pass in theattracting transport arm 12, and is covered with a transport element 16.

Further, the apparatus which includes such a transmission type sensor asshown in FIG. 3 or such a reflection type sensor as shown in FIG. 4 maybe replaced by a yet further apparatus wherein a proximity sensor 20 isinstalled at the location of the stage 13 at which the attraction object11 is to be placed as shown in FIG. 7.

Besides, where the distance detection means for measuring the distanceto the object present in the opposing direction is disposed on theattracting transport arm, the distance of downward movement of theattracting transport art to the attraction object can be recognized byitself. Consequently, if, for example, a servomotor is used for avertically moving the apparatus for the attracting transport arm, sothat even if the height of the attraction object changes, the downwardstroke of the attracting transport arm when the attraction object is tobe attracted can be adjusted readily based on the recognized distance ofdownward movement. This is effective in maintenance comparing with thatwhere the vertically moving apparatus for the attracting transport armemploys an air cylinder. In particular, where the vertically movingapparatus employs an air cylinder, if the height of the attractionobject changes, then time and labor are required for adjustment suchthat the mounted position of the air cylinder is adjusted or the heightof the attraction object on the stage is adjusted.

Further, when the attracting transport arm is horizontally moved from areference position to a position above the predetermined location, thestopping position of the arm is sometimes displaced from thepredetermined location. This arises from the following cause. Generally,coordinates of the position of the predetermined location are determinedas an origin in advance. Then, a moving apparatus for the attractingtransport arm refers to the coordinates of the position of thepredetermined location to calculate a movement amount and moves theattracting transport arm by the movement amount from the referenceposition. However, as transportation is repeated for a long time, thetransport apparatus deteriorates, resulting in displacement of thereference position. In this instance, even if the attracting transportarm is moved from the reference position by the movement amountcalculated referring to the coordinates of the position of thepredetermined location, the stopping position of the arm is displacedfrom the predetermined location. As a result, the attracting transportarm fails to attract an attraction object present at the predeterminedlocation, or even if it successfully attracts the attraction object, itfails to transport the attraction object accurately to a next transportlocation.

According to the present invention, also such positional displacement ofthe arm can be detected. In particular, in a condition wherein anattraction object is not present at the predetermined location, theattracting transport arm is horizontally moved from the referenceposition to the position above the predetermined location. In thisinstance, if rays of light from the light emitting sensor are notreceived by the light receiving sensor, it can be discriminated that theposition of the attracting transport arm is displaced from thepredetermined location. Further, after it is discriminated that thestopping position of the attracting transport arm is displaced in thismanner, the attracting transport arm is horizontally moved in anarbitrary direction until the rays of light from the light emittingsensor are received by the light receiving sensor. Then, the coordinatesof the position when the attracting transport arm is to be moved to theposition above the predetermined location are corrected based on thecoordinates of the position recognized by the moving apparatus for theattracting transport arm when the light receiving sensor receives thelight. Consequently, the positional displacement of the attractingtransport arm from the predetermined location is corrected, and theattraction object present at the predetermined location can betransported accurately to a next transport position. Besides, since thepositional displacement detection element is provided in the nozzle ofthe attracting transport arm, the apparatus is very small in sizecomparing with an alternative apparatus wherein the positionaldisplacement is detected using, for example, a camera.

As described above, according to the present invention, a light emittingelement is disposed either on the rear side of a stage at apredetermined location or on an attracting transport arm. The stage hasa through-hole provided at the predetermined location such that rays oflight from the light emitting element may not be intercepted by thestage. And, a light receiving element for receiving the rays of lightfrom the light emitting element is disposed on the rear side to thepredetermined location or the attracting transport arm at which thelight emitting element is not disposed. On the other hand, a reflectionelement is disposed either on a surface of a stage at the predeterminedlocation or on an attracting transport arm. And, a light emittingelement and a light receiving element for receiving rays of light fromthe light emitting element via the reflection element are disposed onthe surface at the predetermined location or the attracting transportarm at which the reflection element is not disposed. By thisarrangement, since useless upward and downward movements as in the priorart which only employs a pressure sensor need not be performed indiscrimination of whether or not an attraction object is present, theapparatus of the present invention is improved in throughput. Further,since an attraction object can be detected in a vertical direction, alarge space in a horizontal plane is not required for installation of asensor, and also the number of sensors can be reduced comparing with theprior art.

Further, in such an apparatus as described above, also positionaldisplacement of the attracting transport arm can be confirmed. Further,if the apparatus is combined with the prior art which employs a pressuresensor, then whether or not an attraction object is present can bedetected with a higher degree of accuracy. Furthermore, by supplying airof a positive pressure to a vacuum line of the attracting transport armand blowing out the air from the attraction nozzle, it is possible toclean the light emitting sensor or the reflection element disposed atthe predetermined position.

What is claimed is:
 1. An attraction object detection apparatus fordetecting whether an attraction object (11) to be attracted andtransported by an attracting transport arm (12) which is movable invertical and horizontal directions is present at a predeterminedlocation of a stage (13), wherein:said attracting transport arm (12) hasa nozzle hole formed therein in such a manner as to be opened towardsaid stage (13) side and communicated with a vacuum source; a lightemitting element (14) is disposed either on the rear side to saidpredetermined location or in the interior of said nozzle hole of saidattracting transport arm (12); said stage has a through-hole provided atsaid predetermined location such that rays of light from said lightemitting element (14) may not be intercepted by said stage; a lightreceiving element (15) for receiving the rays of light from said lightemitting element (14) is disposed on the rear side to said predeterminedlocation or in the interior of said nozzle hole of said attractingtransport arm (12) at which said light emitting element (14) is notdisposed; and an upper portion of said attracting transport arm (12)including said light emitting element (14) or said light receivingelement (15) disposed in the interior of said nozzle hole forms a sensorunit (19) independent of but connectable to said attracting transportarm (12) by an optical fiber (18).
 2. An attraction object detectionapparatus as set forth in claim 1, wherein said sensor unit(19) issecured at a position opposing to said predetermined location while saidattracting transport arm(12) is so structured as to allow rays of lightfrom said light emitting element(14) to pass thereto.
 3. A cleaningmethod which uses an apparatus as set forth in claim 1, wherein positivepressure air is supplied into a vacuum line from said nozzle hole ofsaid attracting transport arm(12) to said vacuum source to blow out theair from said nozzle hole toward said predetermined location.
 4. Anattraction object detection method which uses an apparatus as set forthin claim 1, wherein, when said attracting transport arm(12) is moved toa position above said predetermined location, if said light receivingelement(15) receives no light, then it is determined that an attractionobject is present, but if said light receiving element(15) receiveslight, then it is determined that no attraction object is present.
 5. Anattraction object detection method as set forth in claim 4, wherein avacuum pressure sensor is provided in a vacuum line from said nozzlehole of said attracting transport arm(12) to said vacuum source, andafter it is determined by said light receiving element(15) that anattraction object is present, said attracting transport arm(12) is moveddownwardly to said predetermined location and performs an attractionoperation to confirm presence or absence of the attraction object againby said vacuum pressure sensor.
 6. A positional displacement detectionmethod for detecting positional displacement of an attracting transportarm (12) using an attraction object detection apparatus for detectingwhether an attraction object (11) to be attracted and transported by anattracting transport arm (12) which is movable in vertical andhorizontal directions is present at a predetermined location of a stage(13), wherein:said attracting transport arm (12) has a nozzle holeformed therein in such a manner as to be opened toward said stage (13)side and communicated with a vacuum source; a light emitting element(14) is disposed either on the rear side to said predetermined locationor in the interior of said nozzle hole of said attracting transport arm(12); said stage has a through-hole provided at said predeterminedlocation such that rays of light from said light emitting element (14)may not be intercepted by said stage; a light receiving element (15) forreceiving the rays of light from said light emitting element (14) isdisposed on the rear side to said predetermined location or in theinterior of said nozzle hole of said attracting transport arm (12) atwhich said light emitting element (14) is not disposed; and when saidattracting transport arm (12) is moved from a reference position to aposition above said predetermined location while an attraction object(11) is not present at said predetermined location, if said lightreceiving element (15) does not receive rays of light from said lightemitting element (14), then it is determined that the position of saidattracting transport arm (12) is displaced from said predeterminedposition.
 7. A positional displacement detection method as set forth inclaim 6, wherein, after it is determined that the position of saidattracting transport arm(12) is displaced from said predeterminedlocation, said attracting transport arm(12) is horizontally moved in anarbitrary direction until said light receiving element(15) receives therays of light from said light emitting element(14), and coordinates ofthe position to which said attracting transport arm is to be movedupwardly above said predetermined location are corrected based oncoordinates of a position recognized by moving means for said attractingtransport arm(12) when said light receiving element(15) receives therays of light.
 8. An attraction object detection apparatus for detectingwhether or not an attraction object(11) to be attracted and transportedby an attracting transport arm(12) which is movable in vertical andhorizontal directions is present at a predetermined location of astage(13), wherein:said attracting transport arm(12) has a nozzle holeformed therein in such a manner as to be opened toward said stage(13)side and communicated with a vacuum source; a reflection element(17) isdisposed either on a surface of said stage at said predeterminedlocation or on said attracting transport arm(12); and a light emittingelement(15) and a light receiving element(15) for receiving rays oflight from said light emitting element(14) via said reflectionelement(17) are disposed on the surface at said predetermined locationor said attracting transport arm(12) at which said reflectionelement(17) is not disposed.
 9. An attraction object detection apparatusfor detecting whether or not an attraction object(11) to be attractedand transported by an attracting transport arm(12) which is movable invertical and horizontal directions is present at a predeterminedlocation of a stage(13), wherein:said attracting transport arm(12) has anozzle hole formed therein in such a manner as to be opened toward saidstage(13) side and communicated with a vacuum source; a reflectionelement(17) is disposed either on a surface of said stage at saidpredetermined location or in the interior of said nozzle hole of saidattracting transport arm(12); and a light emitting element(14) and alight receiving element(15) for receiving rays of light from said lightemitting element(14) via said reflection element(17) are disposed on thesurface at said predetermined location or in the interior of said nozzlehole of said attracting transport arm(12) at which said reflectionelement(17) is not disposed.
 10. An attraction object detectionapparatus as set forth in claim 9, wherein an upper portion of saidattracting transport arm(12) including said reflection element(17) or aset of light emitting element(14) and a light receiving element(15)disposed in the interior of said nozzle hole forms a sensor unit(19)independent of but connectable to said attracting transport arm(12) byan optical fiber(18).
 11. An attraction object detection apparatus asset forth in claim 9, wherein an upper portion of said attractingtransport arm(12) including said reflection element(17) or a set oflight emitting element(14) and a light receiving element(15) disposed inthe interior of said nozzle hole forms a sensor unit(19) independent ofsaid attracting transport arm(12), andsaid sensor unit(19) is secured ata position opposing to said predetermined location, while saidattracting transport arm(12) is so structured as to allow rays of lightfrom said light emitting element(14) to pass thereto.
 12. A cleaningmethod which uses an apparatus as set forth in claim 9, wherein positivepressure air is supplied into a vacuum line from said nozzle hole ofsaid attracting transport arm(12) to said vacuum source to blow out theair from said nozzle hole toward said predetermined location.
 13. Anattraction object detection method which uses an apparatus as set forthin claim 9, wherein, when said attracting transport arm(12) is moved toa position above said predetermined location, if said light receivingelement(15) receives no light, then it is discriminated that anattraction object is present, but if said light receiving element(15)receives light, then it is discriminated that no attraction object ispresent.
 14. An attraction object detection method as set forth in claim13, wherein a vacuum pressure sensor is provided in a vacuum line fromsaid nozzle hole of said attracting transport arm(12) to said vacuumsource, and after it is discriminated by said light receivingelement(15) that an attraction object is present, said attractingtransport arm(12) is moved downwardly to said predetermined location andperforms an attraction operation to confirm presence or absence of theattraction object again by means of said vacuum pressure sensor.
 15. Apositional displacement detection method for detecting positionaldisplacement of an attracting transport arm(12) using an apparatus asset forth in claim 9, wherein, when said attracting transport arm(12) ismoved from a reference position to a position above said predeterminedlocation while an attraction object(11) is not present at saidpredetermined location, if said light receiving element(15) does notreceive rays of light from said light emitting element(14), then it isdiscriminated that the position of said attracting transport arm(12) isdisplaced from said predetermined position.
 16. A positionaldisplacement detection method as set forth in claim 15, wherein, afterit is discriminated that the position of said attracting transportarm(12) is displaced from said predetermined location, said attractingtransport arm(12) is horizontally moved in an arbitrary direction untilsaid light receiving element(15) receives the rays of light from saidlight emitting element(14), and coordinates of the position to whichsaid attracting transport arm is to be moved upwardly above saidpredetermined location are corrected based on coordinates of a positionrecognized by moving means for said attracting transport arm(12) whensaid light receiving element(15) receives the rays of light.
 17. Anattraction object detection apparatus for detecting whether or not anattraction object(11) to be attracted and transported by an attractingtransport arm(12) which is movable in vertical and horizontal directionsis present at a predetermined location of a stage(13), whereinaproximity sensor(20) is disposed at said predetermined location.
 18. Anattraction object detection apparatus for detecting whether or not anattraction object(11) to be attracted and transported by an attractingtransport arm(12) which is movable in vertical and horizontal directionsis present at a predetermined location of a stage(13), whereinsaidattracting transport arm(12) has a nozzle hole formed therein in such amanner as to be opened toward said stage(13) side and communicated witha vacuum source, and distance detection means for measuring a distanceto an object present in an opposing direction is disposed on saidattracting transport arm(12).
 19. An attraction object detection methodwhich uses an apparatus as set forth in claim 18, wherein presence orabsence of the attraction object(11) is discriminated from the fact thatthe distance detected by said distance detection means is differentwhether the object is the attraction object(12) or said stage(13), andalso a distance of downward movement of said attracting transportarm(12) is recognized by said distance detection means.